A. JS. Verrill — Gomparlsons of Coral FauncB. 187 



a barrier as is produced by the Amazonian waters. Indeed, the 

 wonder is that any of the species should ever have passed this bar- 

 rier, except by human agency, unless they, were in existence at a time 

 when the South American continent was less elevated, and when the 

 lower Amazonian valley may have been a great salt-water Bay.* 



It is possible, of course, that some of the smaller and rarer incrust- 

 ing forms, like the Agaricia, may have been carried from the West 

 Indies to Brazil on the bottoms of vessels. If such vessels were kept 

 well out at sea, away from the Amazonian waters, this might occur, 

 for I have seen fine branching specimens of OcvUna, six inches in 

 lieight, as well as other corals, taken from the bottoms of vessels at 

 the Bermudas. But the abundant and larger species, widely dis- 

 tributed on the coast, cannot be accounted for in any such way. In 

 fact, the only ones to which such an explanation could possibly be 

 supposed to apply, would be the Agaricia, Porites astreoides, var., 

 and Millepora alcicornis. But the two latter are too abundant and 

 too widely distributed to make such an explanation seem reasonable. 



Since the course of the ocean currents along that coast is north- 

 ward, any species common to the two faume is far more likely to 

 have been carried northwards from Brazil to the West Indies by 

 their agency, than in the opposite direction. Indeed, it would seem 

 impossible for such species to migrate southward along the northern 

 Brazilian coast. 



Therefore the original home of those species found in both regions 

 must have been the Brazilian coast. 



Most of the Brazilian corals were first described by me in vol. i, 

 ])art ii, of these Transactions, ISOV, but they were not then figured. 

 Prof. C F. Hartt contributed to that paper notes on their habits and 

 distribution. 



The structure, extent, and distribution of the Brazilian coral reefs 

 have been described by Prof. C. F. Harttf and by Mr. R, Rathbun.| 

 Prof. J. D. Dana, in his " Corals and Coral Islands," has made 

 extracts from Prof. Hartt's descriptions (see pp. 140-142, and p. 55 

 of ed. iv, 1890), and on jj. 1 1;) has given a partial list of the corals. 



* It has even been suggested that a direct marine connection between the 

 Atlantic and Pacific Oceans, by the way of the Amazon Valley, may have existed 

 in the Cretaceous and early Tertiary periods. 



f Geology and Physical Geography of Brazil, 1879, pp. 187-214. 



X Notes on the Coral Reefs of the Island of Itapaiica, Bahia, and of Parahyba 

 do Norte, Proc. Bost. Soc. Nat. Hist., xx, pp. 39-41, 1878; Brazilian Corals and 

 Coral Reefs, Amer. Naturalist, xiii, pp. 539-551, 1879. 



